In the field of microfabrication represented by fabrication of integrated circuit devices, photolithographic technology enabling microfabrication with a line width of 0.20 μm or less has been demanded in recent years in order to achieve a higher degree of integration.
A conventional photolithographic process utilizes near ultraviolet rays such as i-line radiation. It is known in the art that microfabrication with a line width of a sub-quarter micron order using near ultraviolet rays is very difficult.
Therefore, use of radiation with a shorter wavelength has been studied for enabling microfabrication with a line width of 0.20 μm or less. As radiation with a shorter wavelength, deep ultraviolet rays represented by a line spectrum of a mercury lamp and an excimer laser, X-rays, electron beams, and the like can be given. Of these, a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), and an F2 excimer laser (wavelength: 157 nm) have attracted attention.
As a resist applicable to the shorter wavelength radiations, a number of resists utilizing a chemical amplification effect between a component having an acid-dissociable functional group and a photoacid generator which generates an acid upon irradiation (hereinafter called “exposure”) has been proposed. Such a resist is hereinafter called a chemically amplified resist.
As a chemically amplified resist, Japanese Patent Publication No. 27660/1990 discloses a composition comprising a polymer having a t-butyl ester group of a carboxylic acid or t-butylcarbonate group of phenol and a photoacid generator. This composition utilizes the effect of the polymer to release a t-butyl ester group or t-butyl carbonate group by the action of an acid generated upon exposure to form an acidic functional group such as a carboxylic group or a phenolic hydroxyl group, which renders an exposed area on a resist film readily soluble in an alkaline developer.
In recent years, in addition to high limit resolution and high process margin, a high sensitivity to radiations is demanded of chemically amplified resists as a factor determining productivity of a photolithographic process.
Reducing the amount of basic substance which is a component of chemically amplified resists is one of the methods of increasing the sensitivity of the chemically amplified resists. This method, however, not only involves a decrease in the amount of acids produced by a photoacid generator, which gives rise to unduly roughened pattern surfaces, but also impairs environmental resistance of the resist such as poor PED stability, which is an indication of line width stability against a fluctuated period of time from exposure to post heat treatment. One method for obviating this problem is to increase the amount of photoacid generator. However, an increased amount of photoacid generator decreases radiation transmissivity through resist films, resulting in a tendency of easily producing a trapezoid pattern profile rather than a desirable rectangular pattern profile.
As a method for improving performance of a chemically amplified resist using an anthracene additive, Japanese Patent Application Laid-open No. 1996-217815 discloses that the addition of anthracene derivatives such as anthracene-9-methanol, anthracene-9-carboxyethyl, and anthracene-9-carboxy-n-butyl to chemically-amplified radiation-sensitive resin compositions is effective in improving particularly a halation prevention effect. Japanese Patent Publication Laid-open 1998-120628 discloses that a chemically-amplified positive-tone resist material containing a carboxylic acid derivative having a tricyclo-aromatic skeleton such as an anthracene skeleton and a carboxyl group protected by an unstable acid group can suppress standing wave and halation.
The methods disclosed in these patents, however, lack investigation into other important aspects such as control of line width variations in resist patterns due to fluctuation of the resist film thickness on a highly reflective substrate (Si-substrate, etc.) and process margins such as improvement of depth of focus. Overall characteristics as a chemically amplified resist for radiation-sensitive resin compositions or positive-tone resist materials are not necessarily sufficient.
An object of the present invention is to provide a positive-tone radiation-sensitive resin composition containing an anthracene-based carboxylic acid component with low sublimation properties and excellent compatibility with other components, the composition exhibiting optimum controllability of radiation transmittance as a chemically amplified positive-tone resist effectively responding to active radiation, particularly to deep ultraviolet rays, effectively controlling line width variation in resist patterns due to fluctuation in the resist film thickness on a highly refractive substrate, and exhibiting good sensitivity, resolution, and excellent focal depth allowance.